This invention relates to a transformerless power inverter to provide from a DC power supply a low impedance source of AC voltage and more particularly to such an inverter that produces a square wave output voltage and uses only NPN transistors or only PNP transistors.
Many inverter circuits have been devised for such purposes as converting DC power to 60 Hz AC power for operating in the field equipment intended to be energized from an electric-utility-supplied power line, or providing an AC power source of a different frequency than 60 Hz. The loads to be driven by inverters are generally either predominantly inductive or predominantly resistive. A capacitor is often included in the inverter to resonate with an intended inductor load to ameliorate the gating and commutating difficulties ensuing from the lagging load currents. The requirements of a gating and commutating means in an inverter depend upon the characteristics of the intended load.
It is an object of the present invention to provide a bridge type inverter with a simple gating/commutating system for producing a square output voltage across any type of load, inductive, resistive or capacitive.